166 STEAM TURBINES

closes the main stop valve; at the same time the oil supply to the relay system
is interrupted and opens a drain on the oil-relay cylinders, admitting also the
oil supply to the top of the oil-power piston. The throttle valve is therefore
closed simultaneously. Provision is made to enable the emergency gear to
be tripped by hand. The oil-pump is placed near the floor, and is attached
to the bearing housing by a special column which makes the pump quite
accessible. The pump is of the rotary type, driven from the main governor
spindle by gears. The oil coming from the bearings runs into a tank in the
bedplate and passes through a strainer into the pump suction. The oil is then

Fig. JQ.—Nozzle Boxes and Connections to Steam Chest
pumped through an oil cooler of the surface-condenser type, and up into the
bearings and oil-relay cylinder. A small hand-pump or steam-driven turbo-
oil-pump is provided to lubricate the bearings when starting up the turbine.
THE METROPOLITAN-VICKERS COMPANY'S DESIGN
The steam turbines built by Messrs. The Metropolitan-Vickers Company
are of the Rateau type generally, with a velocity wheel in the first stage.
Their machines embody many points in design which are claimed to repre-
sent the outcome of the makers' extended experience in the production of
large size units designed to operate under severe steam conditions.
Fig. 19 shows the three nozzle boxes and their connections to the steam
chest. These are the only parts of the turbine subjected to high pressure
and superheat. The boxes consist of steel castings, and are bolted at one
end directly or through pipes to the steam chest, the other end being free to